This invention relates to electronic signal amplifiers and more particularly to such an amplifier wherein a charge pump serves as the load and source of operating energy.
There is shown in FIG. 1 a typical prior art driver circuit in which an NMOS high-side driver transistor 10 controls the current through a load 12 that is connected to the source of the driver transistor 10. The driver 10 and driver load 12 are connected between a voltage energizing terminal 14, at which a positive voltage Vcc may be applied, and a circuit ground point 16. A differential amplifier 18, having a load resistor 19, is connected in a feedback loop between the source and the gate of the driver transistor 10 for establishing a current in the driver load 12, which driver load current is proportional to the input voltage of the feedback amplifier 18 at input terminal 20.
This driver circuit illustrates a problem in prior art circuits wherein it is desired to energize a high current driver transistor from a voltage source (Vcc) capable of supplying the necessary high currents to the load, while at the same time it may be desirable to energize relatively low-power driver-control circuits, such as the amplifier 18 in FIG. 1, from a source of voltage that is much greater than Vcc in order to provide a greater dynamic range of input and output driver-control signals.
This problem is typically solved by providing a second energizing voltage source (not shown) for supplying separately the needed higher voltage to the driver control circuits. The considerable additional expense of providing the second and higher voltage supply source is often avoided leading to compromises in amplifier performance, and therefore driver circuit performance. This additional expense is especially objectionable when the driver transistor and the driver control circuits are to be integrated in a single silicon chip.
It is an object of this invention to provide an amplifier circuit capable of having a greater dynamic range of input and output signals than the magnitude of the supply voltage that is used to energize the amplifier.
It is a further object of this invention to provide such an amplifier as a driver-control-signal amplifier in a low cost integrated circuit wherein both the wide dynamic range amplifier and the driver may both be energized from the same voltage source.